1. Field of the Invention
The present invention pertains to wheeled, movable irrigation systems and more particularly, it pertains to a rotary irrigation system which can be moved in a closed loop path to irrigate relatively large areas of land.
2. Description of the Prior Art
Typical irrigation systems include a ditch and furrow type of irrigation system, a flooding type of irrigation system. The flooding type and the ditch and furrow type of irrigation systems may be used where the fields are relatively level or have a gentle slope. The sprinkling type of irrigation may be used with land which does not lend itself to the other types of irrigation or where the cost of the other systems is relatively high. Sprinkling also has the advantage of causing less crusting of the soil, and, as a result, the water soaks into the soil faster and results in less evaporation of water than when flooding is used. In many areas of the world the sprinkling system is less expensive to build and to operate than the other type of irrigation systems.
Some prior art sprinkling systems include structures wherein the tubing is mounted on a plurality of wheels so that the tubing can be more readily moved from one section of the field to another. Even then it may be necessary to disconnect some of the sections of tubing so that they can be rolled across the field to a new area. Some of these prior art portable irrigation systems use small gasoline motors to supply power to the wheels so that the system can be moved from one portion of the field to another. One portable irrigation system which is arranged to be automatically moved on wheels by motors is shown in a prior U.S. Pat. No. 2,892,466 to Stilwell et al. This patent shows an irrigation system having relatively long lengths of pipe mounted through the hubs of wheels which are spaced at intervals along the pipe line to support the pipe above ground. A motor mounted on a carriage can be coupled to the wheels when the pipe is to be moved from one location to another. The motor causes the wheels supporting the pipe and the pipe to rotate so that the pipe moves across the ground. When the pipe is in the new location, the motor, which provides the power for moving the pipe, is disconnected prior to water being supplied to the pipe.
Other prior art sprinkling systems include structures wherein the tubing is mounted on a plurality of spaced carriages which are moved across the field by a water-powered motor as the field is sprinkled. One water-powered sprinkling system is shown in a prior U.S. Pat. No. 3,590,853 to Haynes. A single water-powered motor provides power to the wheels of each of the carriages to move a long length of pipe across the length of an area being irrigated. Another water-powered sprinkling system is shown in a prior U.S. Pat. No. 3,692,045 to Carr. The system shown in the Carr patent provides a separate water-powered motor for each of the carriages. When the apparatus shown in the Carr patent is connected so as to move in a circle about a central source of water it is very difficult to control the speed of each motor to keep the pipe from bending and being damaged. The carriage farthest from the central pivot point must have a velocity many times as great as the carriage nearest the central pivot point.
Another prior art portable sprinkler system is shown in a prior U.S. Pat. No. 3,536,261 to Van Den Brink. This system includes a standpipe connected to a pressurized water source, a length of sprinkler tubing with one end rotationally engaging the standpipe and with a tractor attached to the free end of the tubing. The tubing is supported above the ground by a series of carriages each having a pair of wheels so that the tubing can be moved about the standpipe. The tractor is driven in a circle about the standpipe. There is no provision for providing a tension on the pipe so that considerable bending of the tubing occurs due to rolling resistance of the supporting carriages. As a result the Van Den Brink system must use heavy and expensive tubing or limit the tubing to short lengths to prevent damage to the tubing. The Van Den Brink system of irrigation also requires at least two wheels for each of the supporting carriages.
Other prior art United States patents which disclose rotating sprinkler systems for irrigating generally circular plots of ground include U.S. Pat. Nos. 2,893,643 to Gordon; 3,259,319 to Wallace; 3,448,927 to Blair; 3,608,826 to Reinke; 3,730,211 to de Laine; and 3,672,572 to Delfs.